A Plant‐Transpiration‐Process‐Inspired Strategy for Highly Efficient Solar Evaporation

The conversion of solar energy into heat for solar steam generation is significant for energy saving and clean water supply. Recent advances in the design and application of photothermal‐based water‐evaporation systems have attracted intense research interest. However, it is imperative to develop a low‐cost and scalable photothermal system with further improved energy conversion efficiency to meet the demand for real‐world applications. Inspired by the natural transpiration process of plants, a wood‐polydopamine‐based photothermal material is developed for solar‐steam generation. Both the wood and polydopamine (PDA) derived from natural products are cost‐effective, biodegradable, and environmentally friendly. The wood–PDA system evaporates thin water film right above the bulk water surface, leading to extremely high efficiencies. Solar steam can be generated only 5 s after light irradiation. The solar‐steam generation efficiency reaches 87% under 1.0 sun. More significantly, an explosive evaporation which bypasses the phase change from liquid to gas is observed on the wood surface under irradiation of more‐intense light. This yields a solar‐steam generation efficiency (calculated by the classic equation) beyond 100% (e.g., 135% under 3.5 sun). It is envisioned that this strategy can be readily applied in practical solar‐evaporation applications due to its simplicity, low cost, and high efficiency.